#!/usr/bin/env python3
# -*- coding=utf-8 -*-
# 题目：画椭圆。


def f1():
    from tkinter import Canvas
    from tkinter import mainloop

    y = 160
    top = y - 30
    bottom = y - 30

    canvas = Canvas(width=400, height=600, bg="white")
    for i in range(20):
        canvas.create_oval(250 - top, 250 - bottom, 250 + top, 250 + bottom)
        top -= 5
        bottom += 5
    canvas.pack()
    mainloop()


f = f1
if __name__ == "__main__":
    f()
